In electroacoustic converters with good bass reproduction, the resonance chamber between the diaphragm and the rear side of the converter must be closed. Such known converters have a fixed rear side, and the volume of this resonance chamber cannot be changed to adjust the sensitivity of the microphone. It has been proposed to provide such converters, e.g. microphones, with a movable piston so that adjustment can be made. This, however, results in the creation of large leaks in the resonance chamber, and this deleteriously affects the bass reproduction of the microphone. There are also problems with the item-by-item handling of the microphones during production.